With the increasing expansion of the Internet, existing IPv4 addresses composing of 32 bits are becoming not sufficient. Accordingly, the IPv6 protocol employing an IP address of 128 bits has been proposed to thoroughly solve the problem of insufficiency of the IPv4 addresses and to make significant improvements on address capacity, security, network management, mobility and quality of service, etc.
Before the IPv6 protocol becomes the main-stream protocol, the IPv4 protocol will be continuously used, thus the coexistence of the IPv4 network and the IPv6 network occurs. In addition, due to imbalance of address allocation, some countries or regions still have enough IPv4 address space for allocation, and the IPv4 network will exist in these countries and regions for a long time. In the predictable future, the IPv4 network and the IPv6 network will coexist for a long time.
The international Internet Engineering Task Force (IETF) has established a specialized NGTRANS (Next Generation Transition) working group to study the problem of IPv4/IPv6 transition and efficient seamless intercommunication. Various transition technologies and intercommunication approaches have been developed at present. One of the typical transition technologies is a dual protocol stack technology. The dual protocol stack technology is the most direct way to make IPv6 nodes compatible with IPv4 nodes, and the objects to be applied comprise communication nodes such as hosts and routers. FIG. 1 shows a system intercommunicating by means of dual protocol stack. An IPv6 protocol stack may be used when an IPv6 node supporting the dual stack protocol is intercommunicating with another IPv6 node, while an IPv4 protocol stack may be used when the IPv6 node is intercommunicating with an IPv4 node. At present, the RFC definitions and the JDK in Java technique use static methods to selectively use an IPv4 or IPv6 address of the destination address. There are the following problems in the above two methods: once a transmitting party transmits, for example, an IPv4 packet, the area through which the packet is transmitted is fixed onto the IPv4 network. In addition, although a host can support the dual stack, the existing RFCs prescribe that priorities of IPv4 and IPv6 are statically set in the dual stack. For example, if it is prescribed that IPv4 has higher priority than IPv6, all the transmitted packets will be IPv4 packets, and the large amount of the IPv4 packets will be forwarded via an IPv4 backbone network. Thus, the situation where the IPv4 network is quite busy while the waste of IPv6 network resource is wasted might occur, and vice versa.
In the prior art, in order to solve the intercommunication problem between the IPv4 network and the IPv6 network, a tunneling technology is also used as the alternative technology for transition from the IPv4 network to the IPv6 network. FIG. 2 is a schematic diagram showing the prior art in which the networks are intercommunicated by means of the tunneling technology. In the tunneling technology, when an IPv6 node C accesses an IPv6 node D, a 6 over 4 IP packet is formed, and then is transmitted through a router X to a router Y via an IPv4 network. the router Y removes the header of the IPv4 packet, and transmits the IPv6 packet to the IPv6 node D via an IPv6 network. Therefore, the IPv6 packet can be transmitted over the IPv4 network by forming an IPv6 tunneling path for transmitting the IPv6 packet between the routers X and Y. However, in the above methods, bandwidth and router resource will be competed between IPv4 traffic and IPv6 traffic.
Therefore, the prior art cannot dynamically select the network with less traffic for transmitting information, based on the traffic in the current networks to efficiently utilize the network resources. Especially, when the traffic in the IPv4 network is too heavy while the traffic in the IPv6 network is very light, or vice versa, the prior art cannot make adjustment in real time on the traffic between the two networks to improve the utilization imbalance between the two kinds of networks.